Suppose on pushing a button an object is to be notified, but it is not known until runtime which object should be notified. Which of the following programming constructs should be used to implement this idea?

class Sample
{
    public int func(int i, Single j)
    {
        /* Add code here. */
    }
}

1. A struct can contain properties.
2. A struct can contain constructors.
3. A struct can contain protected data members.
4. A struct cannot contain methods.
5. A struct cannot contain constants.

1. An attribute can be inspected at link-time.
2. An attribute can be inspected at compile-time.
3. An attribute can be inspected at run-time.
4. An attribute can be inspected at design-time.

1. A class
2. A property
3. A struct
4. A function
5. An interface